Reversed‐phase high performance liquid chromatography determination of ochratoxin a in flour and bakery products

A reversed‐phase high performance liquid chromatography procedure for the analysis of ochratoxin A in flour and bakery products is described. Samples are extracted and purified by the method of Roberts and Patterson followed by further clean‐up by back extraction of the toxin into sodium bicarbonate and re‐extraction into chloroform after acidification. The extracts are chromatographed using a Lichrosorb R P8 10μm column and mobile solvent, 55% acetonitrile in 0.1% aqueous orthophosphoric acid at a flow rate of 1 ml min−1. The height equivalent to a theoretical plate under these conditions is 0.08 mm, the average recovery is 46% and the overall sensitivity of the method is 0.5‐1.0 μg kg−1. When the toxin was added to flour samples which were subsequently baked into bread it was recovered without decomposition; when the experiment was repeated with biscuit baking however, about two‐thirds of the toxin was destroyed or immobilised.